Method and control device for determining a maximum current limit of a battery system having at least two batteries

Abstract

Technologies and techniques for determining a maximum current limit of a battery system having at least two batteries. A separate current is measured at each of the at least two batteries, and a total current is measured of the battery system. For each of the measured separate currents, a current ratio is determined between the measured separate current in question and the measured total current. A maximum individual current limit of the battery system is determined for each of the at least two batteries on the basis of the determined current ratio in question and a nominal maximum current limit of the battery in question. The smallest determined maximum individual current limit is selected as a maximum current limit of the battery system and the determined maximum current limit is provided as a maximum current limit signal. Alternatively, or additionally, the measurements can also be carried out using resistances.

1 - 10 . (canceled) 
     
     
         11 . A method for operating a battery system control unit based on a maximum current limit of a battery system comprising at least two batteries, comprising:
 (i) detecting a respective individual current for each of the at the at least two batteries;
 detecting a total current of the battery system; 
 determining a respective current ratio of the detected individual currents to the detected total current; 
 determining maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined current ratio and a nominal maximum current limit of the respective battery; 
   and/or   (ii) receiving or estimating a respective individual resistance of the at least two batteries;
 receiving or estimating a total resistance of the battery system; 
 determining a respective resistance ratio of the received or estimated individual resistances to the received or estimated total resistance; 
 determining maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined resistance ratio and a nominal maximum current limit of the respective battery; 
   selecting the smallest determined maximum individual current limit as the maximum current limit of the battery system; and   generating a maximum current limit signal based on the determined maximum current limit and utilizing the maximum current limit signal to modify operation of the battery system control unit.   
     
     
         12 . The method according to  claim 11 , further comprising determining a weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         13 . The method according to  claim 12 , wherein the maximum individual current limits are determined from the weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         14 . The method according to  claim 12 , further comprising selecting weighting factors during the determination of the weighted mean value as a function of the total current. 
     
     
         15 . The method according to  claim 11 , further comprising filtering one or more of (i) the current ratios, (ii) resistance ratios and/or (iii) weighted mean values via a low-pass filter. 
     
     
         16 . The method according to  claim 14 , wherein determining the maximum individual current limits comprises determining the maximum individual current limits based on the filtered ratios and/or filtered weighted mean values. 
     
     
         17 . The method according to  claim 11 , wherein the modified operation of the battery system control unit comprises limiting a total current of the battery system based on the maximum current limit signal. 
     
     
         18 . An apparatus for controlling a battery system comprising at least two batteries, comprising:
 a control device operatively coupled to the battery system; and   a plurality of control modules, operatively coupled to the control device, wherein the control device and plurality of modules are configured to   (i) detect a respective individual current for each of the at the at least two batteries;
 detect a total current of the battery system; 
 determine a respective current ratio of the detected individual currents to the detected total current; 
 determine maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined current ratio and a nominal maximum current limit of the respective battery; 
   and/or   (ii) receive or estimate a respective individual resistance of the at least two batteries;
 receiving or estimating a total resistance of the battery system; 
 determine a respective resistance ratio of the received or estimated individual resistances to the received or estimated total resistance; 
 determine maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined resistance ratio and a nominal maximum current limit of the respective battery; 
   select the smallest determined maximum individual current limit as the maximum current limit of the battery system; and   generate a maximum current limit signal based on the determined maximum current limit and utilizing the maximum current limit signal to modify operation of the battery system.   
     
     
         19 . The apparatus according to  claim 18 , wherein the control device and plurality of modules are configured to determine a weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         20 . The apparatus according to  claim 19 , wherein the maximum individual current limits are determined from the weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         21 . The apparatus according to  claim 19 , wherein the control device and plurality of modules are configured to select weighting factors during the determination of the weighted mean value as a function of the total current. 
     
     
         22 . The apparatus according to  claim 18 , wherein the control device and plurality of modules are configured to filter one or more of (i) the current ratios, (ii) resistance ratios and/or (iii) weighted mean values via a low-pass filter. 
     
     
         23 . The apparatus according to  claim 22 , wherein the control device and plurality of modules are configured to determine the maximum individual current limits based on the filtered ratios and/or filtered weighted mean values. 
     
     
         24 . The apparatus according to  claim 18 , wherein the modified operation of the battery system comprises limiting a total current of the battery system based on the maximum current limit signal. 
     
     
         25 . A battery system control unit for controlling a battery system comprising at least two batteries, comprising:
 a control device operatively coupled to the battery system; and   a plurality of control modules, operatively coupled to the control device, wherein the control device and plurality of modules are configured to   (i) detect a respective individual current for each of the at the at least two batteries;
 detect a total current of the battery system; 
 determine a respective current ratio of the detected individual currents to the detected total current; 
 determine maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined current ratio and a nominal maximum current limit of the respective battery; 
   and/or   (ii) receive or estimate a respective individual resistance of the at least two batteries;
 receiving or estimating a total resistance of the battery system; 
 determine a respective resistance ratio of the received or estimated individual resistances to the received or estimated total resistance; 
 determine maximum individual current limits of the battery system for each of the at least two batteries, proceeding from the respective determined resistance ratio and a nominal maximum current limit of the respective battery; 
   select the smallest determined maximum individual current limit as the maximum current limit of the battery system; and   generate a maximum current limit signal based on the determined maximum current limit and utilizing the maximum current limit signal to limit a total current of the battery system, based on the maximum current limit signal.   
     
     
         26 . The battery system control unit according to  claim 25 , wherein the control device and plurality of modules are configured to determine a weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         27 . The battery system control unit according to  claim 26 , wherein the maximum individual current limits are determined from the weighted mean value of the respective current ratio and the resistance ratio. 
     
     
         28 . The battery system control unit according to  claim 26 , wherein the control device and plurality of modules are configured to select weighting factors during the determination of the weighted mean value as a function of the total current. 
     
     
         29 . The battery system control unit according to  claim 25 , wherein the control device and plurality of modules are configured to filter one or more of (i) the current ratios, (ii) resistance ratios and/or (iii) weighted mean values via a low-pass filter. 
     
     
         30 . The battery system control unit according to  claim 29 , wherein the control device and plurality of modules are configured to determine the maximum individual current limits based on the filtered ratios and/or filtered weighted mean values.